Quantifying seasonal variation in total phosphorus and nitrogen from prairie streams in the Red River Basin, Manitoba Canada

摘要

A three-year study (2010,2013 and 2014) was conducted to identify temporal and spatial patterns in phosphorus (P) and nitrogen (N) concentrations and loads in 11 sub-watersheds of the Red River Valley, Manitoba, Canada in relation to human activity on the landscape. Discharge exhibited a strong seasonal pattern in all sub-watersheds with high discharge during snowmelt, generally lower discharge with rainfall-induced peaks during spring, summer and fall, and low or no discharge during winter. Consistent with the hydrologic pattern, nutrient concentrations were highest during snowmelt such that 62% of the annual TP load and 67% of the annual TN load were delivered during the 12-18 day snowmelt period. Partial least squares regression analysis indicated that land use activities such as fertilizer application, livestock density and sewage were critical factors influencing TP and TN concentrations. In contrast, physical aspects such as water temperature and discharge were the primary determinants of TP and TN loads. The finding that stream water nutrients concentrations are associated with human activity on the landscape whereas nutrient loads are largely influenced by hydrologic events suggests that different types of beneficial management practices are needed for protection of instream ecological processes negatively affected by high nutrient levels versus reduction of nutrient export to downstream receiving bodies such as Lake Winnipeg.